Hello there, I'm in need of a recomendation for insulating an exterior bathroom wall (shower enclosure) that is gutted to the 2x3 studs as part of a bathroom remodel. I intend to use cement board and subway tile to finish the enclosure but need to figure out the insulation before I proceed. Because of the 2x3 construction I'm having trouble as I originally figured I would install faced batts; which would have to be compressed to fit thereby affecting the R-value. I've asked around and some suggest hiring a professional to spray closed cell foam, while others have suggested using rigid foam board insulation. I'm not sure how a vapor/moisture barrier or retarder will come into play here. I certainly don't want to grow any beasties in my walls (once I have some again :D.) Thanks in advance!

the minimum require R-value will depend on where you live in the country and your local building codes. here in Mass, the minimum is R-19 which can not be accomplished with fiberglass batts in a 2x3 wall. closed cell spray foam is probably your best bet but most instalers have a very high minimum requirement, usually in the $750 - $1,500 range. but there is a solution to your problem. you can purchase a closed cell spray foam kit ****** for, i think, less than $200. it comes with a full tank, like a barbecue propane tank size, a hose and a nozzle. then you can do it yourself. good luck

i'm guessing the house was built that way. i've seen it once or twice. sometimes you can fir out the wall to make it deeper to accept more insulation but in most cases you can't due to limited space in the bathroom and a prefab shower unit won't fit without moving the other walls.

If you can stand to lose 2-1/2" in the shower, insulate the existing wall with foam board or spray foam. Then build a second wall with 2x3 (which are 2-1/2" wide) with the studs staggered from the existing ones. Insulate that wall, too, with foam board. This way, you reduce the heat loss through conduction that would normally happen through the studs, and you get 6" of insulation.

I didn't install a 2x3 wall. This is a bathroom remodel in a 1950 ranch kit house that was constructed this way. There will not be any plumbing in this wall. It will be insulated, then covered in cement board and tiled with subway tile. There is not room in this bathroom to build out the wall or change dimensions. I'm aware that compressing batts will affect the R-value which is why I'm here seeking another solution (like the rigid foam board or cc foam). Thanks so much everyone.

One last advice before you go: you can take a batt made for 2x4 walls and trim/thin it to fit a 2x3 wall. If you take off about 25% of its width you'll be able to place it without compressing it. The only problem: you will lose some of the insulation effectiveness.

I am doing a similar remodel, except my exterior wall is 2x4 and I plan on using fiberglass insulation. My question is: Is it best practice to just use faced fiberglass insulation and trust that to act as the only vapor barrier? Or do I use unfaced and cover it(and the rest of the shower walls) with a thick (maybe 6mil) plastic sheet before installing the cement board. I assume it is not a good idea to use faced insulation in addition to the plastic sheet.

if it were me id be furring out hte wall to 6".. not only does a wall that thin not meet code for insulation value but it has very little strength to it.. add tile to it and your going to dealing with issues down the road

I know of no ceement board manufacturer that recommends installing it over 16"oc 2x3's. Also the ceement board isn't waterproof. You'll need to add some sort of waterproofing membrane to your shower system. Since you'll have a membrane in the shower area, the insulation there should not be faced. Use only unfaced behind the wet tiled areas.

For more complete information and the ability to post pictures and get answers specific to your home, head on over to the John Bridge Tile Forum. Tell them we said hello. ;)